System and process for persistent marking of flexo plates and plates marked therewith

ABSTRACT

Systems and processes for making a flexo plate, and plates made thereby. Non-printing indicia defined by areas of presence and absence of polymer in the plate floor created using microdots imaged during a LAMS layer imaging step are readable downstream of the washing or other non-cured-polymer-removal step but not to print in the printing step. The non-printing indicia may define a repeating pattern of alphanumeric characters, non-text graphics, or a combination thereof. A difference in growth of plate structures corresponding to different types of microdots may be used for characterizing processing conditions.

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/433,873, filed Jun. 6, 2019, which is a continuation-in-partof PCT Application Ser. No. PCT/EP19/052536, filed 1 Feb. 2019, whichclaims priority to U.S. Provisional Patent Application No. 62/653,972,filed 6 Apr. 2018, all titled “METHOD FOR PERSISTENT MARKING OF FLEXOPLATES WITH WORKFLOW INFORMATION AND PLATES MARKED THEREWITH,” thecontents of all of which are incorporated herein by reference in theirentirety for all purposes.

BACKGROUND OF THE INVENTION

Most contemporary raster image processing (RIP) software, such as, forexample, the RIP available with ESKO Automation Engine software, sold byEsko Software BVBA of Ghent, Belgium, allows creation of Barcodes orQR-codes, which can be added to the image information on a flexographicprinting plate. However, the possibilities of this feature are typicallynot fully utilized.

A typical flexo plate workflow may comprise the following steps:

-   -   1. Processing image information, using a raster image processor,        at a certain screen resolution to obtain an image file.    -   2. Using the processor, combining the image file with other        image files to create an imaging job that covers a full polymer        plate format.    -   3. Imaging the image files onto a Laser Ablation Mask (LAM)        layer on top of a photopolymer plate, by any of various methods        known in the art, thereby creating a mask on top of the plate.    -   4. Curing the rear side of the plate, such as with UVA light, to        build a floor of polymer.    -   5. Curing the photopolymer through the mask on top of the plate,        such as with UVA light.    -   6. Processing the plate to remove non-cured polymer from the        plate.    -   7. Optionally, drying the plate to remove solvent (typically not        performed when a thermal process does the processing).    -   8. Finishing the plate, such as by applying UVA and UVC light.    -   9. Separating the different image files, such as by cutting the        polymer plate into patches on a xy-cutting table.    -   10. Mounting one or more of the plate patches, each of which        embodies one or more image files, to a printing press, such as        on a printing press cylinder.    -   11. Printing physical images on a print-receiving substrate        using the plate in a printing press.

12. Cleaning ink from the plate, removing the plate from the press, andstoring it for future use, such as a reprinting job.

The process steps between image RIPping and printing the physical imagemay be executed in a sequence that is not directly temporal. Some of theconsecutive steps may be delayed by a transport process. For example,between the steps of separating the images on the xy-cutting table andmounting them on a printing cylinder, the plate patches may be shippedfrom a plate manufacturer to a printing facility.

Despite recent advances in automation for plate making, only someprocess steps may be suitable for combination in an automated mannerinto consecutive steps. Hence, many steps may still be executedindependently from the others. As many plate makers have two or moreproduction rows and the equipment for the different production rows maynot be identical, two plates having identical images may run throughdifferent equipment when processed in parallel.

Consequently, the use of workflow markings, if used at all, is typicallylimited to only general information, because attachingequipment-specific parameters to a plate that may be processed ondifferent devices with different parameter settings may not be efficientor useful. Accordingly, parameters are typically set for differentprocess steps manually. Consequently, human errors may cause a certainpercentage of failure, resulting in plate loss, rework and loss ofmoney.

Thus, while it may be known to include some kind of markings on aprinting plate, typical prior art markings only contain information usedfor recognizing the plate in a later process step such as for example,information identifying the Job and Customer name. Plate markings mayalso be used to identify the type of the plate.

One limitation of prior art marking methods for flexo plates is thatthey typically only contain a small amount of information that does notsupport the entire plate workflow. Frequently, the marks are removedduring processing of the plate at a certain point in the workflow,requiring downstream operators to look up plate-processing parametersand manually key them in to the user interfaces of various processingequipment.

Thus, there is a need in the art to eliminate the problem of incompleteand lost information during the passage of a flexographic printing platethrough the plate making workflow, thus improving the central control ofthe plate workflow and helping to avoid operator mistakes, time loss andmoney loss.

SUMMARY OF THE INVENTION

Exemplary embodiments of the invention include a system for making aflexo plate. Exemplary systems comprise a plurality of processingmachines, each processing machine configured to perform one or moreprocess steps in a workflow, including at least an imaging step, acuring step, a washing or other non-cured-polymer-removal step, aprinting step, and optionally, a cutting step, a storage step, or acombination thereof, each processing machine having a controller and atleast one variable operating parameter controlled by the controller. Thesystem includes means for providing machine-readable indicia on theflexo plate. The machine-readable indicia is configured for persistentreadability downstream of the washing (and cutting, where present) stepswithout printing in the printing step. The machine-readable indicia mayembody information including at least a plate identifier andinstructions corresponding to the at least one variable operatingparameter for each of the processing machines or informationcorresponding to an address in computer storage where the informationresides.

The means for providing the indicia may comprise a computer programmedwith instructions for embedding information into a code, such as a2-dimensional code such as a QR code, a barcode, or any machine readablecode known in the art, as well as a computer programmed withinstructions for providing information formatted for embedding into amagnetic stripe or into a chip, such as an RFID chip, capable of beingread by any reader known in the art. The means for providing the codemay further comprise a printer for printing a 2-D code, an imager forembedding the code into a printing plate such that the code will bereadable after plate processing, as well as after the full set of plateprocessing steps to which that plate is configured to be processed. Themeans for providing an RFID code comprises machines for writinginformation onto an RFID-readable chip and machines for writinginformation into a magnetic stripe, as are known in the art, along withany of the processing equipment known in the art required forfabricating an RFID chip and accompanying antenna(s) into a fullyfunctional RFID module or for creating a magnetic stripe and applyingthe stripe to a surface.

As described herein, the indicia may be disposed in a strip of polymerin the plate. In one embodiment, the indicia may be in a portion of theplate that is later cut off. In some embodiments, the indicia may bedisposed on a floor of the plate using areas of presence and absence ofpolymer in the plate floor, and/or by clusters of microdots arrangedaccording to the code.

A plurality of readers are configured to read the indicia on the flexoplate, including at least one reader in communication with eachcontroller of each processing machine. The reader may comprise a mobiledevice, such as a mobile phone, a tablet computer, or the like, having acamera and programmed with instructions to capture an image of the code.The mobile device may have instructions stored thereon for convertingthe image information to the information readable by the controllerand/or information displayed on a display and readable by a humanoperator, or the mobile device may communicate over a network, such as awireless network, to a central processor that converts the image to theinformation readable by the controller. The information for instructingthe controller may be transmitted to the controller by the mobile devicedirectly upon conversion of the image information to such instructions,or by the central processor to the controller upon receipt of the imagefrom the mobile device, or by the central processor back to the mobiledevice, and then to the controller. In other systems, the reader may bedirectly connected to the processing machine and dedicated to thatmachine. In some embodiments, including for mobile devices or dedicatedreaders, the reader may be connected to or in communication with themachine via a wired connection or via a local wireless connection, suchas via Bluetooth technology.

Exemplary controllers are configured to receive from the readerinstructions corresponding to the variable operating parameters storedin or linked to the indicia and to control the processing machine inaccordance with that at least one instruction. Such a controller maycomprise a computer processor, accompanying media for storage ofmachine-readable instructions, and accompanying connections to thevarious portions of the processing machine in the workflow forconducting the process, all of which components are well known in theart. The controller is programmed with instructions for receiving theinformation from the reader corresponding to the variable operatingparameters, and incorporating those parameters into the controlinstructions provided by the controller to the various portionscontrolled thereby. It should be understood that the various portionscontrolled by the controller may be digital or analog devices, and tothe extent necessary, the controller, or converters connected thereto,may convert control information from digital to analog and sensedfeedback or monitoring from analog to digital formats, or vice versa.

In one embodiment, the workflow comprises a proofer, and the informationread from the indicia may include quality information indicative ofprinting properties associated with the plate.

Preferred embodiments also include a tracking controller for theworkflow in communication with each of the plurality of readers. Thetracking controller is configured to receive from each of the pluralityof readers a communication indicative of time and in-process location ofeach flexo plate scanned by the reader. The tracking controller isfurther configured to provide an output indicative of real-time workflowpositions of a plurality of in-process flexo plates. This output may beprovided to a display screen connected to a central processor runninginstructions for operating the tracking controller, and may also beprovided to the mobile devices operative as readers and/or to displaysassociated with any computer connected to a network connected to thetracking controller. The tracking controller comprises a processor andinstructions, stored on computer readable media, for programming theprocessor to receive and store information from the plurality of readersand to process that information into a tracking report output.

Aspects of the invention also include flexo plates created using theprocesses as described herein. Exemplary flexo plates havemachine-readable indicia on the flexo plate that is configured forpersistent readability downstream of washing (and cutting, when present)steps without printing in a printing step of a plate workflow. Themachine-readable indicia embodies information including instructionscorresponding to at least one variable operating parameter for each of aplurality of processing machines or embodying information correspondingto an address in computer storage where the instructions reside, asdescribed herein. The indicia may comprise, for example, a 2-dimensionalcode, such as a QR-code or a bar code, or an RFID module or a magneticstripe. As described herein, the indicia may be disposed in a strip ofpolymer in the plate and/or may be disposed on a floor of the plateusing areas of presence and absence of polymer in the plate floor, suchas may be created by the use of clusters of microdots arranged in theLAMS layer so as to produce structures that rise above the floorslightly but not a printing level. And, as described herein, a firstrendering of the indicia may be located in a first location on the plateand a second rendering of the indicia may be located on a secondlocation on the plate, particularly wherein the first location is in aportion of the plate configured to be cut away from the plate and thesecond location is in a floor of the plate in an imaged area of theplate.

Other aspects of the invention include computer readable mediacomprising non-transitory instructions readable by a machine, theinstructions embodying any of the method and process steps as describedherein. Such instructions may include instructions for coordinating aprocess for making a flexo plate having a plurality of process steps,including, for example, at least an imaging step, a curing step, awashing step, and a printing step, each step performed by a processingmachine having at least one variable operating parameter. The machinereadable instructions may include instructions for providingmachine-readable indicia on the flexo plate, including embodying in theindicia information including at least a plate identifier andinstructions corresponding to the at least one variable operatingparameter for each of the processing machines. The foregoing would beembodied in, for example, software, digital storage media embodying theinstructions, and machines programmed with the software and firmware,for creating the indicia on the plates.

The machine-readable instructions may also comprise software, andmachines programmed with such software, for the tracking controller.Such instructions may include instructions for providingmachine-readable indicia on the flexo plate, including embodying in theindicia information corresponding to an address in computer storage. Theinstructions may also include instructions for storing, in the computerstorage in a location identified by the address, information includingat least one variable operating parameter for each of the processingmachines. The program may also include instructions for receiving acommunication from a reader of the indicia, and instructions fortransmitting variable operating parameters to a corresponding one of theprocessing machines. Such a system may further include instructions forimplementing a tracking controller for the workflow, the trackingcontroller in communication with each of the readers associated witheach of the processing machines, and configured to receivecommunications from a plurality of readers configured to read theindicia from a plurality of in-process flexo plates in the workflow,wherein the indicia also includes a plate identifier. The communicationsreceived from the reader include locations of the in-process flexoplates. The programmed instructions further include instructions forproviding real-time tracking of a workflow position for each of theplurality of in-process flexo plates based upon the communications andinstructions for providing the tracking information as an output.

Still another aspect of the invention include flexo plate processingmachines capable of performing at least one plate processing step in aplate processing workflow, the machines include a controller configuredto receive a communication of one or more variable parameters forcontrolling the plate processing machine from a reader as describedherein. The reader is in communication with the controller configured toread machine-readable indicia on a flexo plate to be processed, theindicia having embodied therein at least instructions corresponding tothe variable operating parameters or information corresponding to anaddress corresponding to a location in computer storage where saidinstructions reside. The reader is configured to read the instructionsembodied in the indicia or at the address corresponding to theinformation embodied in the indicia, and send the communication to thecontroller with the at least one variable operating parameter afterobtaining the at least one variable operating parameter from reading theindicia or from querying the computer storage address corresponding tothe information embodied in the indicia. The controller is alsoconfigured to control the processing machine based at least in part uponat least one variable operating parameter received from the reader.

Yet another aspect of the invention includes readers for use in thesystems and processes for making a flexo plate as described herein. Suchreaders may have at least one detector configured to read the indiciafrom the flexo plate, such as a camera for reading a 2-D code, an RFIDreceiver and transmitter, or transceiver, for sending an RF signal andreceiving an RFID response transmission from an RFID, or a magneticstripe reader. A communication link in the reader is in communicationwith at least a controller of at least one processing machine configuredto perform at least one of the process steps and a central processorconfigured to monitor the workflow. The reader also may have a processorconfigured to process the information read from the indicia, tocommunicate to the controller of the at least one processing machine theat least one variable operating parameter embodied in the indicia orstored at the address corresponding to information embodied in theindicia, and to communicate to the central processor informationregarding the flexo plate read by the reader and a location of thereader within the workflow. The communication to the controller may bedirect communication, or a communication that includes intermediatecommunications between the reader and a central computer. In particular,when the indicia represents an address on a network, the reader may becapable of reading the address, linking to the address, downloading theinformation from the address, and communicating the information to theprocessing machine. The communication to the processing machine may beby any wired or wireless communication method known in the art,including but not limited to those expressly described herein.

In some embodiments, the processes, systems, computer program productsas described herein may be configured to produce plates in whichnon-printing indicia is disposed on a floor of the plate as a presenceor absence of polymer using microdots. One process may comprise imagingthe microdots during a LAMS layer imaging step. The microdots on theresulting plate may comprise a repeating pattern of alphanumericcharacters, non-text graphics, or a combination thereof readable by ahuman and/or machine. The repeating pattern may include alphanumericcharacters embodying information including job number, separation color,version, date, or a combination thereof. In one embodiment, thenon-printing indicia comprises branding information. In anotherembodiment, at least a portion of the non-printing indicia may bederived from at least two different types of microdots, such as acombination that creates visible indicia only in the presence of adifference in growth during curing between one of the types as comparedto another of the types during processing of the plate. The differencein growth may result from suboptimal processing conditions with respectto at least one processing parameter, such as optical focus orcleanness, floor thickness, actinic radiation exposure parameters, ortype of manufacturing equipment.

In another embodiment, the non-printing indicia is used for creating aline for use in alignment of the plate, such as a line positioned on theplate to align parallel to the intended running direction of theprinting plate in the press.

In one embodiment, imaging information for the non-printing indicia maybe stored in a layer of a PDF file. In another embodiment, imageinformation for the non-printing indicia is combined with printing imageinformation by combining two 1-bit image files. The combination of imageinformation for the non-printing indicia may be combined with printingimage information in a Raster Image Processor.

In some embodiments, the processes, systems, computer readableinstructions and resulting plates created thereby, as described herein,may relate to providing the non-printing indicia in the form of one ormore elevations having a plate thickness above a predefined floorheight, wherein the microdots corresponding to the non-printing indiciadefine the one or more elevations. In other embodiments, thenon-printing indicia is provided in the form of one or more depressionshaving a plate thickness below a predefined floor height, wherein themicrodots corresponding to the non-printing indicia define thepredefined floor height. An exemplary method for providing suchdepressions includes the steps of forming a subfloor at the thicknessbelow the predetermined floor height by performing a back-exposure stepat an energy intensity less than that required to create the predefinedfloor height, and then forming the predefined floor height bydistributing a plurality of microdots in locations in which thepredefined floor height is desired and by omitting microdots inlocations in which the depressions forming the indicia are desired.

One embodiment comprises a system for making a flexo plate comprisingprocessing equipment configured to perform one or more process steps ina workflow, the processing equipment having a controller and at leastone variable operating parameter controlled by the controller, includingone or more units of processing equipment configured for providingnon-printing indicia on the flexo plate disposed on a floor of the plateusing microdots. The processing equipment may include one or more of:imaging equipment, curing equipment, washing or othernon-cured-polymer-removal equipment, printing equipment, cuttingequipment, or a combination thereof, and the non-printing indicia isconfigured for persistent readability downstream of the washing or othernon-cured-polymer-removal and optional cutting steps without printing inthe printing step. In some embodiments, the non-printing indicia may bein the form of one or more elevations having a plate thickness above apredefined floor height, wherein the microdots corresponding to thenon-printing indicia define the one or more elevations. In someembodiments, the non-printing indicia is in the form of one or moredepressions having a plate thickness below a predefined floor height,wherein the microdots corresponding to the non-printing indicia definethe predefined floor height.

Another aspect of the invention comprises a flexo plate comprisingnon-printing to indicia disposed on a floor of the plate in the form ofareas of presence and absence of polymer in the plate floor defined bymicrodots. The non-printing indicia may be configured for persistentreadability, such as downstream of washing or othernon-cured-polymer-removal and optional cutting steps, without printingin a printing step of a plate workflow. The non-printing indicia may bein the form of one or more elevations having a plate thickness above apredefined floor height, wherein the microdots corresponding to thenon-printing indicia define the one or more elevations, or thenon-printing indicia may be in the form of one or more depressionshaving a plate thickness below a predefined floor height, wherein themicrodots corresponding to the non-printing indicia define thepredefined floor height. The microdots may define alphanumericcharacters or may define a repeating pattern of alphanumeric characters,non-text graphics, or a combination thereof. The alphanumeric charactersmay embody information including job number, separation color, version,date, or a combination thereof. The indicia may comprise brandinginformation. The non-printing indicia may comprise a line oriented toalign with an element of plate processing equipment and operative tocheck alignment of the plate relative to the element of plate processingequipment.

Some embodiments may include non-printing indicia comprising a pluralityof plate structures derived from processing at least two different typesof microdots. At least a portion of the non-printing indicia maycomprise the plurality of plate structures derived from the at least twodifferent types of microdots in a combination that is visible because ofa difference in size between plate structures derived from one of themicrodot types as compared to plate structures derived from another ofthe microdot types. Such a difference in size may signal a presence ofsuboptimal processing conditions with respect to at least one processingparameter that is not in accordance with a specification. The suboptimalprocessing condition may relate to a processing parameter selected fromthe group consisting of: optical focus or cleanness, actinic radiationexposure parameters, type of manufacturing equipment. At least a portionof the plurality of plate structures derived from the at least twodifferent types of microdots may include at least a first structurecomprising microdots formed from a first, relatively greater number ofpixels and a second structure comprising microdots formed from a second,relatively lesser number of pixels. In such embodiments, deviation ofone or both of the first structure and the second structure from anexpected height above the floor signals the presence of the suboptimalprocessing condition. A plurality of structures comprising microdotsformed from different numbers of pixels may be provided, including atleast one non-printing microdot formed from a number of pixels expectedto form non-printing indicia under optimal processing conditions and atleast one printing microdot formed from a number of pixels expected toform printing indicia under optimal processing conditions, whereinactual height of one or both of the first structure and the secondstructure signals the suboptimal processing condition.

Still another aspect of the invention comprises a non-transitorycomputer readable storage medium having data stored therein representinginstructions for imaging a first plurality of printing dots defining ascreened image for making printing structures on a flexographic printingplate and a second plurality of non-printing microdots definingnon-printing indicia. The non-printing indicia define one or morefeatures selected from the group consisting of: alphanumeric characters,non-text graphics, a repeating pattern of alphanumeric characters, aline, and indicia comprising at least two different types of microdots.The non-printing indicia may comprise at least two different types ofmicrodots including at least one type of microdots having a relativelygreater size configured to be visible on a plate processed under optimalconditions and another type of microdots having a relatively lesser sizeconfigured not to be visible on a plate processed under suboptimalconditions. The non-printing indicia may comprise at least two differenttypes of microdots in a combination configured to be visible on a plateprocessed under suboptimal conditions because of a difference in sizebetween plate structures derived from one of the microdot types ascompared to plate structures derived from another of the microdot types.The instructions relating to the non-printing indicia may be configuredto generate one or more elevations having a plate thickness above apredefined floor height, wherein the microdots corresponding to thenon-printing indicia define the one or more elevations in locations thatdo not provide support for a printing dot. The instructions may insteador also be configured to generate non-printing indicia is in the form ofone or more depressions having a plate thickness below a predefinedfloor height, wherein the non-printing microdots define the predefinedfloor height.

In yet another aspect of the invention, a process for making a flexoplate comprises non-printing indicia disposed on a floor of the plateusing areas of presence and absence of polymer in the plate floor,wherein the non-printing indicia is disposed on a floor of the plate andthe process comprises forming the non-printing indicia via exposure toactinic radiation from a back, non-printing side of the plate. Thenon-printing indicia may include alphanumeric characters, non-textgraphics, a machine readable code, a line, and combinations or repeatingpatterns of any of the foregoing.

The process may comprise providing a primary back exposure and anadditional back exposure. In embodiments in which the non-printingindicia comprise areas of presence of polymer in the plate floor, theprocess may comprise forming the plate floor using the primary backexposure, and forming the non-printing indicia raised above the platefloor using the additional back exposure. In embodiments in which thenon-printing indicia comprise areas of absence of polymer in the platefloor, the process may comprise forming a subfloor corresponding to aheight of the non-printing indicia using the primary back exposure, andforming the plate floor using the additional back exposure.

The primary back exposure may be performed before the additional backexposure, and the additional exposure may be performed after the primaryback exposure but before the front side exposure. The primary backexposure may be provided by a first exposure source and the additionalback exposure may be performed by a second exposure source. The firstexposure source and the second exposure source may be spaced apart fromone another in a fixed relationship, in which the process comprisescausing relative movement between the plate and the first and secondexposure sources. Front side exposure may be provided by a thirdexposure source spaced from a front side of the plate in a fixedrelationship relative to the first and second exposure sources.

The additional back exposure may be provided by an LED matrix comprisinga plurality of individual LED units, a digital light processing (DLP)unit, or by directing radiation from one or more sources through amasking component, such as a liquid crystal diode (LCD) matrix or afilm. The additional back exposure may be provided by directingradiation to an imaging plane disposed above the plate floor. Thenon-printing indicia may comprise structures comprising a plurality ofindividually definable microdots or may be continuous embossedstructures.

The additional back exposure and the primary exposure may be providedsimultaneously, or the additional back exposure may be provided in adifferent step than the primary exposure. The additional back exposuremay be performed over an area of the plate smaller than an entire areaof the plate, in which case the process may comprise selecting an areaof the plate for receiving the additional back exposure that avoids thenon-printing indicia interfering with printing features.

Another aspect of the invention comprises a system for making a flexoplate by curing a photopolymer plate with actinic radiation, the systemcomprising a front side exposure system configured to direct actinicradiation to a front side of the printing plate for creating printingfeatures defined above a floor of the plate, and a back side exposuresystem configured to direct primary actinic radiation and additionalactinic radiation to a back side of the printing plate for creating thefloor and non-printing features raised or depressed relative to thefloor. The back exposure system may comprise an LED matrix for providingthe additional actinic radiation, and may further comprise opticsconfigured to focus radiation from the LED matrix to a desired planerelative to the plate, which plane may be above the plate floor.

In some embodiments, the back side exposure system comprises a primaryback side radiation source configured to provide the primary actinicradiation and an additional back side radiation source configured toprovide the additional actinic radiation. The primary back sideradiation source and the additional back side radiation source may bespaced apart from one another at a first spacing in a fixedrelationship, in which case the system may further comprise means forcausing relative movement between the plate and the primary andadditional back side radiation sources. The front side exposure systemmay comprise a front side radiation source spaced from a front side ofthe plate in a fixed relationship at a second spacing relative to theprimary back side radiation source, and the means for causing relativemovement may be further configured to cause movement between the plateand the front side radiation source. The first spacing and secondspacing may be adjustable.

In some embodiments, the back exposure system may comprise a DLP matrixconfigured to supply the additional actinic radiation. In otherembodiments, the back exposure system may comprise a source of actinicradiation and a masking component—such as a liquid crystal diode (LCD)matrix or film—disposed between the source and the plate. In suchconfigurations, the source is configured to emit actinic radiationtoward the masking component and the masking component is configured totransmit the additional actinic radiation to the plate.

Yet another aspect of the invention comprises a flexo plate, the platehaving printing structures formed of cured photopolymer having aprinting level above a floor of the plate and configured to print in aprinting step of a plate workflow; and non-printing indicia structuresconfigured for persistent readability without printing in the printingstep of the plate workflow. The non-printing indicia are disposed on afloor of the plate in the form of areas of presence or absence of curedphotopolymer relative to the plate floor, and may comprise embossed,continuous features not defined by discrete microdots.

Still another aspect of the invention comprises a non-transitorycomputer readable storage medium having data stored therein a first setof instructions for imaging a first plurality of printing dots defininga screened image for making printing structures on a flexographicprinting plate via exposure to actinic radiation from a front side ofthe printing plate and a second set of instructions for imagingnon-printing indicia via exposure to actinic radiation from a back sideof the printing plate, the non-printing indicia defining one or morefeatures selected from the group consisting of: alphanumeric characters,non-text graphics, a machine readable code, a line, and combinations orrepeating patterns of any of the foregoing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram depicting an exemplary embodiment of theinvention comprising a workflow process with a tracking controller.

FIG. 2A is a schematic diagram depicting a plate having indicia read bya reader in communication with a controller in an exemplary workflowsystem embodiment of the invention.

FIG. 2B is a schematic cross sectional diagram of an exemplary flexoplate having first and second indicia in accordance with one embodimentof the invention.

FIG. 3 is a flowchart depicting an exemplary process of the invention.

FIG. 4 is a plan schematic view of a portion of an exemplary printingplate comprising repeating indicia at a non-printing depth comprising awatermark in accordance with an embodiment of the invention.

FIG. 5 is a cross-sectional schematic view of a portion of an exemplaryprinting plate, showing the LAMS layer and mask openings therein forcreating printing and non-printing information.

FIG. 6 is a plan schematic view of a portion of an exemplary printingplate showing printing and non-printing information, wherein thenon-printing information is in the form of elevations above the platefloor.

FIG. 7A depicts image information corresponding to various types ofdifferent exemplary microdot patterns.

FIG. 7B is a plan view of exemplary non-printing indicia formed bydifferent microdot structures in which the different microdot patternshave resolved to indistinguishable differences in microdot structure onthe plate floor, rendering the indicia invisible.

FIG. 7C is a plan view of exemplary non-printing indicia formed bydifferent microdot structures in which the different microdot patternshave resolved to distinguishable differences in microdot structure onthe plate floor, rendering the indicia visible.

FIG. 8 is a perspective view schematic illustration of an exemplaryraster pyramid for microdots created from single microdots.

FIG. 9A is a perspective view schematic illustration of an exemplaryraster pyramid for microdot structures created from clusters ofmicrodots.

FIG. 9B is a perspective view schematic illustration of an exemplaryraster pyramid for a plurality of tiles of microdot structures createdfrom clusters of microdots of a single size.

FIG. 9C is a perspective view schematic illustration of an exemplaryraster pyramid for a plurality of tiles of microdot structures createdfrom clusters of microdots in a first, relatively larger size and asecond, relatively smaller size.

FIG. 9D is a perspective view schematic illustration of an exemplaryraster pyramid for a plurality of tiles of microdot structures createdfrom clusters of microdots in a first, relatively larger size; a second,relatively smaller size; and a third, intermediate size.

FIG. 10A is a plan view of an exemplary set of printing pixels in a1-bit printing image file.

FIG. 10B is a plan view of vignettes placed around each of the printingpixels of FIG. 10A.

FIG. 10C is a flowchart describing an exemplary method for combiningprinting and non-printing files to avoid disrupting image information inthe highlights.

FIG. 11A is a side view of an exemplary set of targets for indicatingplate floor height.

FIG. 11B is a plan view of the exemplary set of targets of FIG. 11A.

FIG. 12 is a cross-sectional schematic view of a portion of an exemplaryprinting plate, showing the LAMS layer and mask openings therein forcreating printing and non-printing information, wherein the non-printinginformation is in the form of depressions below the plate floor.

FIG. 13 is a schematic illustration of a system for creatingnon-printing information on the floor of the plate from the back side ofthe plate using UV LEDs.

FIG. 14 is a schematic illustration of a system for exposing a printingplate having a main, front side exposure, a primary back side exposure,and an additional back side exposure.

FIG. 15 is a schematic illustration of a system for creatingnon-printing information on the floor of the plate from the back side ofthe plate using a wide area or linear radiation source and a maskingcomponent disposed between the radiation source and the back of theplate.

FIG. 16 is a schematic illustration of a system for creatingnon-printing information on the floor of the plate from the back side ofthe plate using a digital light processing (DLP) unit.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, FIG. 1 schematically illustrates aworkflow 100 having a plurality of process machines 110, 120, etc. eachconfigured to perform one or more process steps in the workflow ofcreating a printing plate.

As depicted in FIGS. 2A and 2B, one aspect of the invention provides amarking method and structure for flexographic printing plates 200 andtheir precursor states, which enables the association of up-to-allprocess-relevant information to the plate itself by attachment ofindicia 212, 214 to the plate, and thereby enables controlling up-to-allprocess stages using this information. Preferably, the processingmachines used for the plates are also configured with or incommunication with a reader 220 configured to read the marks, andconfigured to receive process parameters required for the plate to beprocessed and to report the status of plates being processed to acentral control computer 170, based upon information derived fromreading the marks. Embodiments of the system thus enable monitoring andcontrol of the complete platemaking process for all plates in theworkflow chain from order intake to plate storage after printing.

While the parameters for RIPping and imaging are provided directly froma computer by a data file, the parameters for the remaining steps areideally attached to the plate in accordance with aspects of theinvention. Exemplary steps in the workflow may include a UV exposurestep performed by a UV exposure system 110, a thermal or chemicalprocessing step performed by thermal or chemical processing apparatus120, a finishing step performed by finishing apparatus 130, a cuttingstep performed by cutting apparatus 140, mounting one or more cutportions of a plate onto a substrate with a mounting apparatus 150, andprinting in a flexo process with a printer 160, using the substratehaving the plate portions mounted therein. Additional steps may also beincluded in the workflow at the beginning or end, and interposed betweenany of the steps specifically depicted. For example, an imaging steptypically precedes the UV exposure step, an ordering step typicallyprecedes the imaging step, and a storage step follows the printing step.The blocks associated with each processing step are exemplary only, anda single machine may perform steps related to multiple blocks, ormultiple machines may together perform the steps illustrated in a singleblock. Some steps depicted may be optional.

This attachment to a plate 200 may be accomplished, for example, usingmachine-readable indicia 212, which may be a 2D code such as a QR-codeor a barcode, a radio-frequency identification (RFID) module, or amagnetic strip. One form of machine-readable indicia may comprise a 2Dcode in the form of alphanumeric characters readable by a human as wellas configured to be captured by a camera and processed using textrecognition software known in the art, such as is depicted in FIGS. 5and 6 . Such embodiments have the advantage of providing a code on theplate that can be read and interpreted by both a human operator and amachine. The RFID module may be inserted into the polymer before orafter curing at a spot of solid image area on the plate where thepolymer is to be cured (and thus retained on the fully exposed plate).In exemplary embodiments with a magnetic strip, the strip is preferablyattached to the rear side of the plate on the dimensionally stable PElayer of the plate, where the strip is positioned to contact a readinghead mounted on the processing machine as the plate is processed. Themagnetic strip may be attached as a completed strip formed by any methodknown in the art, or may comprise a magnetic ink dispensed directly ontothe rear side of the plate. Although the indicia 212 is depicted as a QRcode in the figures, it should be understood that the QR code in thefigures is intended as a schematic representation application to any ofthe types of indicia described herein, or their equivalents.

Although certain indicia have been explicitly described, the term“indicia” is intended to have its broadest meaning of “an indication” or“distinguishing mark,” without limitation to how that indication or markis capable of being read, and thus the “equivalents” of the indicia asexpressly described are intended to be broadly construed. While certainmachine-readable indicia or codes may take advantage of formats that areexclusively machine readable to permit a large volume of information tobe stored in a small amount of space, it should be understood that theterm “machine readable,” as used herein to refer to indicia and codes,is not limited to indicia having a format that is exclusivelymachine-readable. Those of skill in the art will appreciate that humanreadable alphanumeric information is also machine readable by a readerequipped with suitable optical character recognition (OCR)functionality, and that the hardware and software for providing suchfunctionality is well known in the art and becoming more ubiquitous. Forexample, many highway toll authorities now use character recognition oflicense plates as an equivalent to, a substitute for, or supplement toRFID pass technology. Furthermore, machine vision systems and humanoperators alike can also be trained to read non-alphanumeric graphicsymbols to convey information that can be universally understood (e.g.the graphic symbols denoting recyclable materials or laundry carerecommendations). Thus, it should be understand that the terms “indicia”and “machine readable” are intended to be broadly interpreted toinclude, without limitation, in addition to the other types of indiciadiscussed in detail herein, printed or otherwise visible alphanumeric orgraphical information configured to be read and comprehended by humanoperators as well as machines, as well as combinations of indicia thatare exclusively machine readable with indicia that is both human andmachine readable. One advantage of using machine-readable indicia thatis also at least partially human readable, is that an experienced humanoperator may be able to process and act upon at least some codes fasterthan it would take that same operator to enlist the assistance of amachine.

In some embodiments, the code for a printed code, such as a bar code ora QR code or printed indicia comprising text and/or graphics readable bya human or machine, may be added during ripping the image file and isthus included in the content of the image information, such as in the.LEN file or encrypted LENx file associated with an Esko PlatePrepworkflow. Adding a code to an image file may be accomplished using, forexample, Esko DeskPack™ barX software, which software comprisesmachine-readable instructions embodied in storage media, such as a harddrive, a flash drive, or any type of media, as is well known in the art.As described herein, the imaged information may be provided in the formof non-printing structures on the plate floor formed using microdots,including in the form of a non-printing watermark derived from the useof non-printing microdots in a printing portion of the plate. Suchstructures formed from microdots may be created on a flexo plate usingan Esko® XPS exposure system.

The following examples refer to QR-codes as the exemplary informationstorage technology, but the invention is not limited to any particularinformation storage technology, and is applicable to any informationstorage technology known in the art capable of conveying the amount ofinformation required to practice embodiments of the invention, and inparticular, to any of the storage technology expressly described herein.

In preferred embodiments, all processing equipment 110-160 in theworkflow 100 are provided with or connected to a scanner or otherinformation capture device, herein referred to as a “reader,” whichallows reading the indicia to obtain the associated plate processparameters. Thus, in preferred embodiments, before starting the processor processing step, process information is scanned from the plate andthe relevant process parameters are set accordingly. For example, wherethe indicia 212 comprises a visible code, such as a QR code or abarcode, the reader 220 may comprise a mobile device, such as a mobilephone, a handheld computer, a tablet, or the like. Although reader 220is depicted as a “phone,” it should be understood that the figure isintended to be a schematic representation of any applicable reader, andmay comprise any type of reader known in the art suitable for readingthe indicia provided. Thus, for example, where code 212 comprises anRFID tag, the reader comprises an RFID reader, and where code 212comprises a magnetic stripe, the reader comprises a magnetic stripereader. The technologies and apparatus associated with reading2-dimensional printed codes, magnetic stripes, and RFID tags are wellunderstood in the art. Reader 220 is connected to controller 230 of theapparatus for performing the identified process step. The connectionbetween the reader and the controller may be a wired or wirelessconnection. An exemplary wireless connection may comprise a localwireless network running on computers local to a facility in which theprocessing step is located, or may be a network connected to a globalinformation network or wireless communication network. Controller 230may be programmed with instructions for translating the informationderived from the indicia into the information required to set thecorresponding parameters of the processing equipment, or the translationinstructions may be contained in the reader. The information derivedfrom the reader may be embedded directly in the indicia, or the indiciamay comprise information corresponding to an address in computer storageon a network where the information resides in communication with thereader and the controller. The information corresponding to the addressmay be a URL, a process identifier, or a unique plate identifier. In anembodiment in which the information is a unique plate identifier, thesystem may be configured to use the unique plate identifier to find thecorresponding instructions, such as using by using the plate identifierto query a lookup table that resides at a known address. In embodimentswhere tracking specific plates is not of interest, and where theprocessing instructions corresponding to the universe of plates to beprocessed have only a limited number of permutations, the informationcorresponding to the address may be a process identifier rather than aunique plate identifier. In such embodiments, the process identifier maybe used for querying a corresponding lookup table of processinstructions corresponding to each process identifier. In embodiments inwhich the instructions are embedded in the identifier, the indicia mayalso further embody a unique plate identifier, wherein the plateidentifier may be used for tracking the plate or identifying the plate,such as with a mobile device, as described herein later.

Process information may include, for example and without limitation: thejob name, customer name, printer's name, plate type, plate thickness,back exposure energy, preferred back exposure time, main exposureenergy, preferred main exposure time, number of main exposure cycles,plate processing speed, plate processing temperature, plate cuttingpath, plate cutting speed, and the like.

In one embodiment of the invention, process information is stored in theindicia 212, such as a QR code. Reading a QR code from a plate can beperformed with an existing QR-code reader (i.e. a code scanner) known inthe art. For example, a model C5PC003 code scanner from Wenglor issuitable for omnidirectional scanning of 1D and 2D codes, including butnot limited to 1D codes (commonly referred to as “barcodes”), such asCode39, Code93, Code128, UPC/EAN, BC412, Interleaved 2 of 5, Codabar,Postal Codes, Pharmacode, and 2D codes, such as DataMatrix ECC 0 . . .200, PDF417, Micro PDF417, QR-Code, Micro QR-Code, Aztec Code, GS1Databar, and Dot code. The indicia used for providing the information isnot limited to any particular type of code. In order to increasecontrast and readability of the code on the plate, light from a lightsource (not shown), such as a light typically associated with a cameraflash for a mobile device, may be applied from the bottom or the top ofthe plate. In preferred embodiments, process parameters for differentstages are embodied directly in the code such that each individualprocessing unit can derive instructions directly from the code on theplate without having to connect to a network. In other embodiments, thecode may comprise a computer storage address where the processinformation is stored, and the reading step comprises reading theinformation, connecting to the storage address embedded in theinformation such as via a hyperlink, reading the information from thestorage address, and communicating relevant stored information to theprocessing machine.

In one embodiment of the invention, illustrated in FIGS. 2A and 2B, theinformation is at least initially stored in a first indicia location212, such as in the form of a QR code, which location is disposed on atest strip 210 adjacent the image area 205 of a flexo polymer plate 200.This test strip may also contain register and color proof marks forsetting up the press. While, preferably, the register marks and othermarking on the test strip (and thus also the QR code, when placed onsuch a test strip) stay on the polymer plate together with the image forthe entire life of the plate, in some embodiments it may be necessary tocut the test strip away from the plate to avoid printing the informationon the test strip, such as a QR code, on the printing substrate.Embodiments to address this situation are discussed herein later.

Providing code information that is persistently readable during allprocess steps (e.g. imaging, curing, washing, printing, and optionalcutting and storage steps) is a challenge in connection with washingprocesses associated with flexo plates, because most washing processesare solvent-based. The solvent not only removes non-cured portions ofthe flexo plate polymer, but it also removes ink of the type typicallyused on printed labels and marker pens. Thus, one aspect of theinvention relates to providing a code configured to survive a washingstep by making the code part of the image or by inserting informationinto cured portions of polymer. For example, an RFID device may beinserted into the cured portion of the polymer mechanically, or amagnetic strip may be disposed on the surface of the dimensionallystable layer on the rear side of the polymer plate where it ispositioned to be read by a magnetic card reader head as is known in theart. Such an RFID device or mag strip must be capable of surviving thedownstream processing steps, however. While adding coded information tothe image enables persistence past the washing step, in some embodimentsit is undesirable for the codes to be printed. Thus, preferredembodiments may include codes embodied in the plate in a way that ispersistent past a washing step, but not printed in a printing step. Inone embodiment, the code is added only in the plate floor, such that thedetails do not reach the printing surface, as described below. Inanother embodiment, the code is placed in a location beyond the desiredportion of the printed image (e.g. in a test strip) and, in some cases,the code is transferred to another location prior to or during a cuttingoperation, as described below.

As used herein, the “washing” step may refer to anynon-cured-polymer-removal step that removes non-cured polymer from theplate. Such a “washing” process may include a traditional solvent (orwater) washing step, or may also include a thermal method, such as thosecommonly associated with DuPont™ Cyrel® FAST Thermal Workflow orMacDermid® LAVA® plates, as known to those of skill in the art. Thus,the phrase “washing step” as used generally herein should be understoodto refer to any non-cured-polymer-removal step, absent explicitreference to specific washing processes.

Indicia Formed of Non-Printing Structures

In some embodiments, to keep the information in the code on the plate200, instead of being located on a plate top surface 202, the 2D code,such as a QR-code 214, may be positioned in the plate floor 204. Theplate floor is built by polymer that has been cured from the backside ofthe plate, but it is not intended to print, thus the thickness of thefloor stays below the level of the printing top surface of the polymer.

Although not limited to any particular method for providing the indicia,there are several preferred ways for providing indicia structures intothe polymer. One preferred method is to provide the indicia via UVexposure through an imaged mask, such as via direct imaging in the mask.This method may place sunken structures on the printing surface level,or microdots that produce elevated structures on the floor ordepressions relative to the floor. Another method is laser engraving,which may provide sunken structures below either the printing surfacelevel or the floor level. Yet another method is to mill sunkenstructures below either the printing surface level or the floor level.

In some embodiments, a code 212 that resides below the top (printing)surface 202 of a test strip 210 of the plate 200 during some processsteps may be transferred from the top surface to the floor surface 204.For example, code 212 may be scanned by the reader and the code or codeimage stored in a data file and then that data file may be used forinstructing the cutting of a reproduction of the code image 214 into afloor portion 204 of the image area 205 of the plate while the plate ison the cutting table. As depicted in FIG. 2A, code 214 depicted in alighter shade is intended to represent its location on the floor of theplate where it will not cause an image corresponding to the code toprint when the top surface is used for printing. As depicted in FIG. 2B,code 214 (solid lines) may be cut into floor 204, such as formed bylaser engraving or cutting with a milling head.

Microdots and Watermarks

In another embodiment, the code 214 (dashed lines) may be formed on topof the floor surface 204, such as formed using microdots in the LAMSlayer during the exposure step, such that the code rises to a levelabove the floor 204, but below the top printing level 202. A particularmethod for storing a code on the plate floor comprises using microdots,such as are disclosed in EP 1 557 279 B1, incorporated herein byreference. FIGS. 4-12 depict embodiments relating to this aspect of theinvention. The use of non-printing microdots for raising the printingfloor to provide support for marginally printable image features is alsowell known, such as is to described in U.S. Pat. No. 7,126,724. Themicrodots as generally described, herein, however, are not intended toprovide support, and are typically disposed in locations far enough awayfrom printing dots so as not to provide such support. Rather, themicrodots are used for creating non-printing indicia havingfunctionality as described further herein. Some embodiments describedherein may include a combination of microdots providing support and notproviding support, however.

The term “microdots” as used herein primarily refers to small maskopenings in the LAMs layer of a flexo plate, wherein each opening is notwide enough to grow a printable screen dot in isolation (under normalpower), but clusters of them (or single pixels with sufficient boost)are operable to raise the plate floor level. The term microdot may alsorefer to any dot used in any imaging step by any process capable ofcreating a non-printing dot structure on a plate, including but notlimited to direct curing processes and non-LAMS mask-based processes. Asused herein, the term “microdot” may be used to refer to a feature inthe image information used by the imager for creating the plate or maskstructure, as well as the plate structures formed thereby. In someembodiments, a cluster of microdots may be used to form sections ofelevated floor relative to other sections of the floor that remainnon-elevated and arranged in a formation resembling the dark and lightsections in a QR-code or a barcode. In other embodiments, described inmore detail below, microdots may be used to form the floor and anabsence of such microdots may be used to provide depressions in thefloor. In still other embodiments, microdots may also be used to createa combination of elevated and depressed structures relative to apredetermined floor level. The microdots in the mask result inmicrostructures (elevations or depressions) in the exposed plate.

For example, FIG. 5 depicts an exemplary cross-section of a portion of aprinting plate 700, a floor 713, printable structures 711 formed fromscreen dots 701, and non-printing structures 712 formed from microdots702. FIG. 4 depicts an exemplary portion of printing plate 500 showingfloor regions 504 in white, printable patterns 506 comprised ofprintable screen dots in black and non-printing indicia 508 in gray.Non-printing indicia 508 includes text 507 and graphics 509 in arepeating pattern that forms a non-printing “watermark.” As depicted inFIG. 4 , the watermark comprises a graphic 509 and text 507 that repeatsin a grid pattern (comprising 3 columns and 3 rows as depicted in FIG. 4, but not limited to any particular configuration. Text 507 includesinformation regarding the job (e.g. “Job Number 1234”), the separationassociated with the plate (e.g. “Cyan Plate”), the version of the plate(e.g. “Version 1”) and a date associated with the plate (e.g. “18 Apr.2019”). The invention is not limited to any particular type of text orgraphics, however, and may include branding information such as logos ortrademarks (e.g. graphic 509 is a graphic logo associated with Esko)identifying the plate owner, plate designer, the maker of the workflowsystem that created the plate, or the like. Although depicted in FIG. 4with watermark 508 including both non-text graphical indicia 509 andtextual indicia 507 readable by a human (and a suitably configuredmachine vision system coupled to a processor programmed with characterrecognition capability), the watermark may comprise only non-textgraphics or only textual indicia. Graphical indicia may include any typeof indicia as disclosed herein, including but not limited tomachine-readable codes including but not limited to barcodes and QRcodes.

The term “watermark” is used herein as an analog to the originaldefinition of the term for the identifying images or patterns on paperthat appear as various shades of lightness/darkness when viewed bytransmitted or reflected light (at certain angles or atop a darkbackground), caused by thickness or density variations in the paper.Such watermarks are often visible in the paper constituting an originaldocument, but not in reproductions (e.g. photocopies) made from thatpaper. By analogy, the non-printing watermark formed in accordance withembodiments of the invention may be more visible under certainconditions (e.g. reflected light at a certain angle) and comprise avariation in thickness of the plate, with the markings not reproduced inprinted matter made by the subject plate.

As depicted in FIG. 6 , text indicia 802 is visible relative to thefloor of the plate, and may be more visible in light transmitted throughthe plate or reflected at certain angles. The watermarked indicia 802,having a relatively lesser height above the floor, is distinguishablefrom printable text 801, having a relatively greater height above thefloor. Watermark structures using microdots give the ability to addnon-printing information such as trademarks and logos to the polymerplate that identify the source of the plate, processing equipment, orother entities involved in the workflow to create the plate that isready to print. Because using microdots create a challenge in RIPpingthe image file, imaging the mask, and curing the plates, the presence ofmicrodots organized into visible structures may also serve as proof thathigh-quality equipment was used for manufacturing the printing plate,and may provide quality information regarding the manufacturing process.Thus, for example, microdot-based indicia may be used not only toprovide proof of the plate's origin or proof the plate was made with acertain type of equipment, but also proof that the manufacturing processwas successfully completed, including proof the floor thickness iscorrect, and proof the plate is/was mounted/aligned properly (e.g. onthe printing cylinder).

One method for using microdot-based indicia for showing proof of correctfloor thickness is to create a plurality of test target structuresdesigned to have a mixture of dots in the target structures stableenough and not stable to survive the washing process, such as the targetstructures depicted in FIGS. 11A and 11B. For example, a set ofconcentric rings 1300 may be formed of a first number of pixel dotsforming a central ring or circle 1302, a second number of pixel dots ina first intermediate ring 1303, a third number of pixel dots in a secondintermediate ring 1304, a fourth number of pixel dots in an outermostring 1305, and so on, with each level increasing in size (e.g. 2×2, 3×3,4×4, 5×5 . . . pixels). Differences between numbers pixels in sequentialdots may be greater (e.g. 2×2, 4×4, 5×5 . . . ) or lesser (e.g. 1×2,2×2, 2×3, 3×3 . . . ) than the example above, as dictated by needs fordistinguishing between levels and number of different levels provided.In another embodiment, a set of block target structures may comprisesuccessively increasing numbers of pixel dots in each of blocks 1312,1313, 1314, 1315, and so on, similar to the different numbers of pixelsfor ring structures. In the exemplary structures, an expected numberthat is fewer than all of the blocks/rings should have an expectedgrowth level (e.g. a measured height that reaches the printing surface)in a perfect height floor. If fewer than the expected number ofblocks/rings reach the expected height, it signifies that the floor istoo low. If more than the expected number of blocks/rings reach theexpected height, it means the floor is too high. Although depicted withblocks or rings with four different sizes of dots for illustration,embodiments with more or fewer than four may be provided. For example,embodiments with nine different sizes may be preferred. The variation inmask opening may be adjusted to a given plate and a target floorthickness that produces dots of the middle field (e.g. 5^(th) block in a9-block field) standing at the expected height (e.g. the printingsurface of the plate) when the floor thickness is according to thecorrect specification. In the nine-block example, if the floor is toothick, the fourth or third field may reach the surface, and if the flooris too thin, the first field reaching the surface may be the sixth orseventh block. Embodiments in which the microdots surround normalprinting dots that are supposed to grow to the printing surface of theplate may also be provided.

The range of acceptable floor height may include heights in which someof the structures have noticeably different visibility than others, andembodiments may be derived in which the differences between properconditions and improper conditions may be detectable based uponvisibility or non-visibility of the different fields, rather thanrequiring an objective measurement in every instance. For example, asdepicted in the side view of FIG. 11A, the concentric ring 1303 isdepicted as being present above the floor with a height that is lessthan the height of rings 1304 and 1305. Although depicted with a totalof four structures/rings, it should be understood that more or fewerstructures may be provided, with a minimum of two structures required(one that should have the expected height, and one that should not havethe expected height in a perfectly made floor). The examples providedherein are for illustration only. While other methods for providinghuman readable information on the plate floor, e.g. by laser engravingof the polymer after the plate has been processed, as discussed hereinand in the applications to which the subject application claimspriority, methods other than imaging with microdots require additional,time-consuming process steps and machinery.

As understood to those of skill in the art, microdots are clusters oftiny mask openings in the LAMs layer of the photopolymer plate, theamount of UV light (or other actinic radiation) is not great enough forcuring structures on the plate floor that reach the top of the plate,but it is sufficient to create structures on the plate floor that aretypically visible.

One method for making microstructures can be described with reference toFIG. 5 . Polymer plate 700 comprises a LAMs layer 710, a polyethylenebacking layer 730, and photo curable polymer 720 in between. Hatchedportions depicted in FIG. 5 are those portions of the plate that havebeen cured through the mask openings 701 and 702 and the backing layer730 and that will stay on the backing layer after LAMs and non-curedportions of polymer have been removed in a washing process.

Actinic radiation (e.g. UV light) entering the plate through the backinglayer forms the so-called floor 713 of the plate. This is a solid layerof polymer that builds the base for the structures as further describedherein. The thickness of each structure is determined by the amount oflight energy the polymer receives. At the places where regular maskopenings 701 are located, printing structures 711 grow from the floor tothe top of the plate. In places where microdot mask openings 702 arelocated, non-printing structures 712 grow on the floor but do not reachthe top of the plate, and thus do not transfer ink later in the printingprocess.

Several parameters have influence on the growth of non-printingstructures on the plate floor. For example, the microdot mask openingmust have a diameter that is small enough not to grow printing dots thatreach the plate's printing surface, but wide enough to allow asufficient amount of energy to enter the polymer to cause polymer chaingrowth. The mask opening may be modified by the number of pixels in theimage that build each microdot mask opening or by the laser power forindividual pixels used in imaging the mask, such as using ESKO pixelboost technology. The distance from one opening to another affects theamount of energy per surface unit that can enter the plate. The curingradiation (e.g. UV light) intensity and exposure time, and number ofrepeating exposure steps also affect the structure growth for a givenmask opening size. The sensitivity of the photopolymer also has aninfluence on structure formation, and the washing parameters have aneffect on the structures that remain on the plate, particularly formicrodot structures not polymerized to the plate printing surface.

In one embodiment, the microdots are used to underlay a brand name asproof of the plate's origin. Thus, for example, as depicted in FIG. 6 ,the entire floor surface of the plate may be covered by a sourceindicator 802 (“ESKO”) formed of non-printing microdots. As depicted inFIG. 6 , the ESKO mark is rotated by 45° with respect to the plateedges, but such types of branding are not limited to any particularorientation, repeat pattern, or the like. Printable details 801(“Printed Text and Images”), formed of structures that will print whenthe plate is inked and placed in contact with a substrate for receivingthe ink, are also shown in FIG. 6 for contrast.

The presence of non-printing structures may also be used for proofingthe correct and complete execution of all process steps with qualifiedprocessing equipment. Because the creation of non-printing structurescan be very demanding, incorrect parameter settings in one of theprocess steps may result in missing parts of the printing andnon-printing details. Because printing details change continuously withthe artwork to be printed, missing parts are often difficult torecognize in a standard plate based only on printing details. While itis known in some instances to print test patterns for monitoring thecorrect processing of the plates, these patterns typically correspond tothe printing (as compared to non-printing) details.

Failure of a single process step may affect the result of thenon-printing details in the final plate. Accordingly, in one embodimentof the invention, non-printing detail, which will only appear on theplate floor correctly when all process steps (imaging, UV curing,washing) are executed properly, are added to the image file tofacilitate recognition of shortcomings in plate processing.

For example, non-printing detail may be added in the form of text thatreads, “Focus properly set.” If the focus of the laser beam is not setproperly, most of the standard artwork is still visible in the LAMsmask, but fine details will get lost. In particular, the fine maskopenings corresponding to microdots will get lost without correctfocusing of the laser beam. The characteristics of the microdots forming“Focus Properly Set” may be selected so that this non-printing text isnot readable if the focus is not properly set.

In another embodiment, text stating, “Focus not properly set” may beincluded in the image file to be formed with microdots. Referring toFIGS. 7A and 7B, in this embodiment, the word “not” may be imaged intothe LAMs by using a first type of microdots 901 that are surrounded by asecond type of microdots 902. The grid as depicted in FIG. 7A representspixels with each block representing a pixel of the smallest sizecorresponding to the nominal image file resolution of the printingsystem. On the left side are depicted conventional mask openings 900 forcreation by conventional imaging (certain beams in vertical columns ofpixels are turned on for a number of pixels and ablate several pixels ofopenings into the LAMs layer). The ratio between ablated and not ablatedLAMs determines how much cured polymer growth will be achieved on thefloor during an exposure step.

This works also for boosted single pixels 901 as shown on the upperright field of FIG. 7A. Only single pixels are switched on but the laserpower is turned up/boosted so much that the mask opening are much widerthan the image file resolution would suggest. This produces a similarratio between ablated and not ablated LAMs, as do the conventionallyimaged mask openings.

In a third variation, the same ratio between ablated and non-ablatedLAMs may be created by much smaller single pixels 902, if their quantityper surface unit is increased as shown in the lower right area of FIG.7A.

Under ideal processing conditions, all types of microdots grow the sameamount of polymer on the plate floor. If the imaging system is notproperly in focus, however, the bigger mask openings 900 and 901 willstill create similar wide-mask openings, whereas the smaller dots 902will not. They will produce either significantly smaller openings or noopenings at all. Either way, the ratio between ablated and not ablatedportions of the LAMs layer actually made in the mask by openings 902 incomparison to the openings 900 and 901 is changed.

In an embodiment in which the word “not” is produced by the third typeof microdots 902 and is surrounded by microdots of one of the first twokinds 900 or 901, the word “not” will be invisible (as schematicallydepicted in FIG. 7B with the outline of the text characters shown in thefigure for illustrative purposes only, but which outline may notactually be visible on the plate) as long as the polymer growth isidentical for all types of mask openings. If the plate has been imagedout of focus, the smaller microdots will produce lower or no growth atall, and the word “not” will become visible, as schematically depictedin FIG. 7C.

The foregoing principle may be similarly applied to exposure parameters.For a properly executed exposure procedure, a balance in growth ofnon-printing structures on the floor for two different kinds of maskopenings results in no differentiation between the two types ofopenings. Whenever the exposure procedure is not properly executed, adifference in growth between the two different non-printing structureson the floor creates a visible marker. This principle may also be usedfor detecting dirt on optical surfaces of the imaging system. If theoptics get dirty, the focus spot becomes blurry and microdots with manyrelatively smaller openings do not cause the same amount of mask openingas fewer, relatively larger microdots. The same principle can be used toshow that certain equipment was used for the manufacturing of theprinting plate, by which use of equipment of a quality capable ofproducing both types of microdots will result in no visible differencebetween the two types of dots when formed on the plate, whereas use oflower quality equipment will produce such a difference that appears inthe form as visible text.

Another application for non-printing structures on the floor may be forchecking the alignment of a plate on the printing cylinder. For thispurpose, as shown in FIG. 6 , a straight line 803 may be formed on thefloor in an orientation parallel to the circumference of the printingcylinder. During mounting the plate, or later in the press, this linecan be used to check the correct parallel alignment of the plate withrespect to the printing cylinder or sleeve.

Thus, as described herein, microdots are created by openings in the maskby ablating clusters of pixels in regular distance in the LAMs layer, orby ablating only single pixels in the LAMs and boosting the laser powerfor ablation such that the total width of the mask opening is adjustedto the desired value, such as for example, by using a Gausian Beamprofile for the ablation.

Various method may be used for providing the image information for thenon-printing structures in the image file used for controlling ablationof the mask.

In one embodiment, a 1-bit image file (e.g. a LEN-file of thenon-printing image) may be combined additively with another 1-bit imagefile that contains screen information for suitable microdots. Thecombination of non-printing image and screen is conjunctive in that onlyoverlapping pixels of non-printing image and screen produce a pixel inthe resulting file. The screen may comprise conventional screen dotsbuilt from clusters of pixels or single pixels later boosted duringimaging of the LAMs. The combined non-printing image/screen file is thencombined with the 1-bit is image file that contains the imageinformation for the printing structures (which itself may comprise acombination of an image file and a screen). The combination ofnon-printing and printing 1-bit image files is disjunctive, in thatpixels from both files are included in the resulting combination file,regardless of overlap. This process may be performed on the fly duringthe imaging process.

To avoid undesired changes in the highlights of the image, however, itmay be desirable to block non-printing dots from overlapping withcertain details of the printing files. An exemplary method for combiningfiles is shown in the flowchart depicted in FIG. 10C. Starting with theoriginal 1-bit printing file and original 1-bit non-printing file instep 1270, an adjusted 1-bit printing file is created by placingvignettes around the image information in the original 1-bit printingfile in step 1272 (as described in more detail below with reference toFIGS. 10A and 10B. Then, the vignetted 1-bit printing file is combinedwith the original 1-bit non-printing file in step 1274 with a functionthat dictates that if a bit is “ON” in the vignetted printing file, itwill be turned OFF in the non-printing file, thereby creating acorrected 1-bit non-printing file. The corrected 1-bit non-printing fileis then combined with the original 1-bit printing file to create thefinalized file for RIPping, in step 1276.

One method for placing vignettes around the image information in the1-bit printing file is depicted in FIGS. 10A and 10B. FIG. 10A shows theimage information intended to be printed, comprising a plurality ofprinting pixels 1201, 1202, 1203, 1204, 1205, 1206, 1207. FIG. 10B showsthe vignetted 1-bit printing file with a number of concentricperipheries 1210, 1220, 1230, 1240, 1250, 1260 of additional pixelsdisposed around each printing pixel in the printing file (labeled onlyrelative to pixel 1201 to reduce clutter). The number of concentricperipheries is preferably greater than the widest distance (in pixels)between highlight screen dots in the printing file. The concentricperipheries overlap and build a solid area (as illustrated in FIG. 10B,bounded by periphery 1260) of pixels surrounding the printing details inthe printing file.

Another method of creating such vignettes in a vector-based image fileis to increase the thickness/diameter of the pen used to draw theprinted objects substantially enough to create objects that buildvignettes around the original objects in the file.

The vignettes may be created during ripping the image files or later ina merger application (e.g. the ESKO Merger) before a job is sent to theexposer of the imager (e.g. a CDI Imager).

Image information is often provided by PDF files. PDF files oftencontain different layers (e.g. for different ink colors). Accordingly,the non-printing image may be contained in a dedicated layer of the PDFfile. This image is then ripped by the RIP with the screen of microdots.

As it is advantageous to create different microdot structures in themask, the PDF layer for non-printing images may contain gray levelinformation. Different gray levels may be assigned to different microdotsizes or different numbers of microdots per surface unit by using araster pyramid tile. FIG. 8 schematically illustrates a raster pyramidfor microdots created from single dots. FIG. 8 depicts a matrix of pixellocations in the horizontal plane, and different boost levels in thevertical axis. These dots are boosted according to the desired maskopening; hence, the grey level controls the number of dots per surfacearea and the boost amplitude of the laser power. For simplicity, thepyramid depicted in FIG. 8 shows only three different levels of microdotdensity. A similar pyramid is illustrated in FIG. 9A depictingconventional imaging of microdots without boosting. FIG. 9A depicts amatrix of pixel locations in the horizontal plane, and different maskopening sizes of non-boosted dots in the vertical axis. Here, also, thegrey level controls the number of dots per surface area and the size ofthe dots. Remarkably, if the imaging and curing system are properlyworking, the three different gray levels in each of FIGS. 8 and 9 shouldall lead to a similar amount of plate floor growth for all three sizesof the non-printing structures, because dots formed by greater boostingor a greater number of pixels have a corresponding reduction in thedensity of mask openings (e.g. dots per surface area). If some aspect ofthe overall system is not working properly, however, the lowest levelareas may have less growth in contrast to the highest level. Thus, useof different grayscale non-printing structures may be used as anindicator of system performance.

As further illustration, FIGS. 9B-9D illustrate six tiles at differentgray levels. At the level depicted in FIG. 9B, only six (6) maskopenings 901, each comprising, e.g., 5×5 pixels, produce respectivegrowth. The level depicted in FIG. 9C comprises structure growthassociated with 36 mask openings 902 of 3×3 pixels. The level depictedin FIG. 9D comprises structure growth associated with 117 mask openings903 of 1 pixel size. Structures 903 associated with 1 pixel maskopenings will disappear if, for example, the focus is not set properly,whereas despite such an improper setting, structures 901 associated withmask openings corresponding to the 5×5 pixel clusters will still beproduced.

In another embodiment of the invention, indicia may be created in theplate floor as an inverse structure to those previously described, inform of a depression at a predetermined height below the floor, ratherthan a predetermined elevation above the floor. Referring now to FIG. 12, there is shown a photo curable polymer plate 1200 comprising a LAMslayer 1220 and a backing layer 1230. Hatched portions depicted in FIG. 5are those portions of the plate that have been cured through the maskopenings 1211 and 1210 and the backing layer 1230 and that will stay onthe backing layer after LAMs and non-cured portions of polymer have beenremoved in a washing process. Similar to the plate depicted in FIG. 5 ,mask openings 1211 produce printing structures 1221 at a printing heightof the plate. Plate 1200 also includes indicia formed by depressions1222 having a lower height than the floor 1223. One exposure process formaking such depressions is to create a first subfloor 1215 at arelatively lower height than the desired final floor by using less backexposure energy than is required to create the height of the desiredfinal floor 1223. In a second step, areas of the desired final floor1223 are formed via the main exposure step using microdot openings 1210in mask 1220. In locations in which the desired inverse indicia 1222 islocated, no mask openings (microdot or printing) are formed in portions1212 of the mask 1220.

The advantage of using depressions rather than elevations is that itavoids any accidental printing of elevated structures on the floor inlocations in which those elevations may interfere with desiredhighlights in the printing area. In one embodiment, a constant screen ofmicrodots is combined disjunctively with the printing image informationto create the normal floor (e.g., pixels already turned “on” based uponimage information remain “on,” and pixels corresponding to microdots areturned “on” only in locations previously “off”). At places wherenon-printing indicia in the form of depressions are located, themicrodot screen is omitted (and the corresponding pixels remain “off”).In a more elaborated embodiment, microdots may additionally be arrangedin concentric circles around certain printing screen dots (e.g. to formnon-printing support dots in highlight areas, based on imageinformation), as suggested in EP 1 557 279 B1.

Although described above with respect to an exemplary process ofcreating plate structures arising from microdots in a LAMS layer, itshould be understood that the invention is not limited to use inLAMS-based processes. Any process known in the art for creating aprinting plate may be used for creating non-printing indicia asdescribed herein, including but not limited to exposure of photopolymerplates by actinic radiation in any range of wavelengths, includingplates created by direct imaging or using masks imaged by any processknown in the art.

Back Side Exposure

In another embodiment, non-printing structures may be added to the floorof a printing plate using a display or matrix pattern generator,including after ripping and imaging the mask. This method may beparticularly useful in applications for use on plates made on older,low-end equipment, and in some embodiments, may run completely separatefrom the underlying plate production process.

In this embodiment, illustrated in FIGS. 13-16 , curing radiation isintroduced from the rear, non-printing side of the plate, where the backexposure is applied. Before, or preferably after, the primary backexposure is applied, an additional exposure is applied using an imagingsystem comprising an actinic radiation source and any method of creatinga spatial variation of the radiation intensity suitable to create animage of desired resolution. Exemplary systems may include:

-   -   a UV-LED Matrix 1340 controlled to form images, letters or        logos, such as is described in more detail below and illustrated        in FIG. 13 ;    -   a masking component 1560, such as a film or liquid crystal diode        (LCD) matrix that carries image information, disposed between a        UV radiation source 1540 (e.g. matrix of UV LEDs, one or more        fluorescent tubes) and the rear of the plate, as illustrated in        FIG. 15 , wherein the masking component transmits UV radiation        only at locations where logos or letters have to be created on        the plate floor and blocks UV radiation transmission in all        other locations; and    -   a Digital Light Processor (DLP) 1640 comprising a plane of        digital mirrors that is illuminated by a UV radiation source        1660 imaged into the rear side of the polymer plate, with the        image plane preferably located between the floor and printing        surface of the plate, and more preferably, slightly above the        floor.

It is advantageous in the back side exposure embodiments to focus the UVradiation on a plane slightly above the floor level (e.g. at a levelwhere the top of the non-printing structures is desired). FIG. 13 showsa preferred radiation path geometry that can be used with a matrix ofLEDs 1340 used for exposing plate 1320, which comprises a layer ofphotopolymer 1320 on top of a backing sheet 1330. FIG. 13 depicts curedphotopolymer in the form of floor 1322 and features 1321 a,b 1323 a,braised above the floor. As is understood in the art, the photopolymerextends in a layer from backing sheet 1330 to at least the top of thehighest raised feature 1321 a,b prior to exposure, exposed portions ofthe photopolymer are sufficiently cured to resist being washed away in awashing step, and then are all that remains after performance of thewashing step. FIG. 13 depicts a cured and washed plate and the apparatusfor curing the plate schematically together for illustration, but as iswell understood by those of skill in the art, the exposure step forcuring the polymer occurs before the washing step that results in theplate with visibly defined features as depicted.

Radiation 1342 emitted by the matrix is preferably focused in the plane1370 slightly above the expected position of the floor inside thepolymer plate. Each LED 1341 in matrix 1340 may have integrated opticsthat concentrates its radiation. One or more additional imaging optics1350 may be used to image the radiation emitted by the plane of the LEDmatrix into the desired plane 1370 on, in, or above the polymer plate.The resulting plate has printing dots 1321 a, 1321 b raised a first,relatively higher, printing level above floor 1322, made by front sideradiation curing polymer through holes 1301 in mask 1300, andnon-printing features 1323 a, 1323 b, raised a relatively lower,non-printing level above the floor, made by back side radiationexposure.

The back side radiation exposure may be controlled, such as withcontroller 1390, to form graphic patterns, such as alphanumericcharacters, logos, QR codes, barcodes, or any type of indicia known inthe art, by turning individual LEDs 1341 in LED matrix 1340 ON or OFFduring relative movement between the LED matrix and the plate.Controller 1390 may be the same controller used for creating the frontside exposure, or a different controller or control module. As depictedin FIG. 13 , each schematic graphic corresponding to an individual diode(e.g. 1341) is labelled ON or OFF in the row of text below it. An OFFdiode does not provide additional exposure, whereas an ON diode providesadditional radiation exposure sufficient to make a non-printing dot.Although depicted as ON or OFF, in embodiments in which a singleexposure pass is used, diodes labelled OFF may have no additionalexposure, but may have a baseline exposure intensity sufficient to formthe floor, and diodes labelled ON may have an intensity corresponding tothe baseline intensity plus the additional radiation desired to createnon-printing dots. Because the non-printing elements are not intended toreceive ink, the non-printing features are not limited to “dots,” suchas are commonly used for holding ink and printing, but rather may becontinuous features not formed by discrete dots. Thus, the radiationprovided by the diodes may be pulsed at a frequency sufficient to formdiscrete dots, or may be turned on and off in a fashion that createslines, solid areas, or the like.

In embodiments in which the non-printing image information is imposedusing a masking component 1560, the masking component may be a film orLCD matrix having transparent and non-transparent areas. The maskingcomponent 1560 may be the same size (e.g. width and length) as thepolymer plate (or the combination of source 1540, masking component1560, and optics 1580 (optional) may project an image that is the samesize as the polymer plate, or any desired size). In otherconfigurations, the masking component may only cover (or only create aprojection that covers) less than the full area of the plate, and theoverall system may be positionable to create non-printing indicia inspecific desired locations, which locations may be coordinated, such asvia controller 1590 which may have information about printing andnon-printing information, to correspond to locations on the platelacking printing features. Controller 1590 is depicted connected tocomponent 1591, which schematically depicts the back exposure unit as awhole, and to component 1592, which schematically depicts the variouscomponents, well known in the art, that create the front exposure mask(which may be film, a LAMS layer, etc.). The masking component 1560 mayhave a multitude of markings (e.g. brand logos), such that the markingsmay be distributed throughout the polymer plate floor like a watermark,as described generally herein. The method may be implemented in a singleexposure step without a need to move the plate relative to the UV source1540 and/or masking component 1560. The source 1540 emits radiation 1542that passes through transparent (or relatively more translucent) areasor holes in the masking component 1560 and is blocked by opaque,non-transparent (or relatively less translucent) areas, and isoptionally focused by optics 1580 (in some embodiments), such that theradiation forms non-printing features 1523 a, 1523 b in the photopolymerabove the floor 1522 of plate 1520. Plate 1520 is also depicted with abacking layer 1530, as is known in the art. Printing features 1521 a,1521 b may be formed by any method known in the art, typically byexposure to actinic radiation through holes 1501 in mask 1500, asdepicted in FIG. 15 . In embodiment in which the masking element hasrelatively less translucent and relatively more translucent areas, therelatively less translucent areas may be used for forming the floor,whereas the relatively more translucent areas may be used for formingthe non-printing indicia in a single step, or a series of steps, inwhich the full or partial primary exposure for forming the floor andfull or partial additional exposure for forming the non-printing indiciaare performed simultaneously.

For printing plates having front-side images comprising a significantamount of screened artwork, the non-printing image information may beadvantageously imposed only at locations on the plate where no printingdetails are present, to avoid changes in size of highlight screenprinting dots. Accordingly, it may be advantageous that the system forrear-side imaging non-printing information on the plate floor bemoveable around the dimension of the polymer printing plate. Coordinatesfor moving the rear-side imaging system may be established and storedusing XY-tables. It should be understood that the non-printing imageinformation imposed from the rear side is typically independent from theimage information imposed in the main exposure. For example, to theextent it may be known in the art to provide addressable back exposurebased upon front side image information to enhance highlights, as isdisclosed generally in U.S. Published Application No. 20100028815 toZwadlo, the present invention does not apply back exposure for thepurpose of in any way enhancing the front exposure. Rather, the backexposure as described herein is imposed based upon non-printable imageinformation to create non-printable features that do not affect (enhanceor degrade) printability of the printing features. To the extent theback-side imposed non-printing information has any relationship to thefront-side imposed printing features, the non-printing information maybe coordinated with printing information to avoid the non-printingfeatures affecting the printable image features. Thus, an aspect of theinvention may include a controller configured to identify gaps in theprintable information for identifying best locations to impose thenon-printing features and/or for coordinating the front-side andback-side imposed information so that the non-printing features do notaffect the printing features. For example, back side, non-printinginformation may be specified in a repeating pattern that is modified bya controller programmed to evaluate the back-side, non-printinginformation against the front-side printing information and to modifyportions of the back-side, non-printing information that would affectthe front-side printing information, if not adjusted, such as bydeletion or changing its location.

In one embodiment, such as using an XPS UV exposure unit made by ESKO,generally described in U.S. Published Patent Application US20180210345A1and illustrated schematically in FIG. 14 , it may be sufficient toprovide only a single row of LEDs 1410 facing the rear of the plate 1420having the same width W as the XPS UV Head 1450 facing the front of theplate, and mounted parallel to the back side exposure head 1440. Whilethe primary front and/or back exposure heads are moved along the plate1420, the individual LEDs 1410 in the row of LEDs are additionallyturned on and off by controller 1490 according to the image informationcorresponding to the non-printing image, thereby adding additionalcuring energy to the plate and forming additional non-printingstructures. Although depicted as a single controller 1490, the systemmay comprise multiple control modules collectively configured to createthe relative movement between the radiation sources and the plate incoordination with modulation of the radiation emissions in accordancewith the desired image information. Thus, in some embodiments, theprimary back exposure may be provided by LEDs 1440 and the additionalexposure for creating the non-printing image information may be providedby a second back side source 1410.

Other embodiments may omit the second back side source 1410, in whichcase both the primary and additional back side exposure may be providedby back side exposure unit 1440. In such embodiments, the additionalexposure may be provided by one or more dedicated passes with the backside exposure unit solely for providing the additional exposure, or theadditional exposure may be provided in the form of additional intensityfor selected LEDs corresponding to the desired additional exposure,while the remaining LEDs provide an exposure at an intensity intendedonly to provide a normal floor depth. It should be understood thatexposure using only a single back side exposure unit for both primaryand additional back side exposure may constitute multiple passes offractional amounts of the total amount of intensity desired for eachlocation on the plate. The intensity provided by the LEDs in suchfractional exposures may include both a fraction of the primary and afraction of the additional radiation on one or more passes for selectedLEDs, one or more passes may comprise only the additional fraction oronly the floor fraction for selected LEDs, or a combination thereof.

As depicted in FIG. 14 , the second back side source 1410 may be spacedfrom the primary back side LED exposure head 1440 by a distance d2 suchthat in the direction of travel T of the sources relative to the plate,a time delay is imposed. The distance d2 between heads 1410 and 1440 maybe adjustable, which may, for example, permit variation in delay betweenthe two heads at constant speed, or a consistent delay time at differentspeeds. As depicted, the spacing (e.g. distance d2) between heads 1410and 1440 in the direction of travel may be less than the spacing (e.g.distance d1+d2) between heads 1450 and 1440, such that the platereceives in sequence, the primary back side radiation from head 1440,additional back side radiation from head 1410, and then front sideradiation from head 1450. Although shown with head 1410 being smallerthan head 1450, which may be preferred in some embodiments, the relativesize, spacing, and location of heads 1410 and 1440 is not limited to anyparticular configuration. Although depicted as linear sources, such asmounted to a carriage (not shown) that may move relative to plate 1420,the sources may form less than a full linear width of the plate and mayalso move perpendicular to the direction of travel T to cover the fullplate.

Although only one exposure configuration is depicted in FIG. 14 , any ofthe exposure configurations disclosed in U.S. Published PatentApplication US20180210345A1 may be modified to include additional backexposure for forming non-printing elements by any method as describedherein. In particular, the configuration depicted in FIG. 15 may also beimplemented in which source 1540 comprises an LED matrix of individualLEDs in an array that covers the full width and length dimensions of theplate. Thus, relative motion between the plate and the back side sourcemay not be required for exposure of the back surface of the plate.Likewise, systems in which the front source also comprising an LEDmatrix of individual LEDs in an array that covers the full width andlength dimensions of the plate may be provided, in which case relativemotion is not required for either front side or back side exposure.

Individual LEDs in any of the LED arrays or matrices as described hereinmay include multiple species of LEDs, each species having a differentcenter wavelengths, and may be spaced in any pattern desired, such as isdescribed in U.S. Provisional Application No. 62/839,171, titledAPPARATUS AND METHOD FOR EXPOSING PRINTING PLATES USING LIGHT EMITTINGDIODES, filed Apr. 26, 2019, and incorporated herein by reference.

In the system depicted in FIG. 16 , like the embodiments of FIG. 13 andFIG. 15 , plate 1620 (comprising photopolymer disposed on backing plate1630) is exposed from the back side to provide additional radiation formaking non-printing features 1623 a, 1623 b raised above floor 1622 to arelatively lower level than printing features 1621 a, 1621 b. Theprinting features are created by any method known in the art, typicallyusing front side exposure through mask 1600 with holes 1601. In thesystem depicted in FIG. 16 , the back side radiation is supplied by DLP1640 illuminated by a UV radiation source 1660 onto image plane 1670 andcontrolled by controller 1690. The workings of DLP systems are generallyunderstood to those of skill in the art and are not detailed furtherherein. This embodiment is not limited to any particular DLPconfiguration.

Like the front and/or primary back exposure, which may be applied inseveral steps, the additional radiation for creating with thenon-printing information may be provided in several steps, either incombination with the normal back exposure, or independently from theprimary back exposure. In embodiments in which the primary back exposureis provided at the same time as the additional radiation for creatingthe non-printing structures, corresponding radiation source emissionsintended to provide only the primary back exposure may be provided at afirst baseline intensity, and radiation source emissions correspondingto non-printing information may be provided at an intensity greater thanthe baseline intensity.

While referred to primarily herein in connection with UV radiation, anyradiation source capable of emitting actinic radiation operable to curea corresponding photopolymer may be used. The invention is not limitedto the methods for providing radiation as described in detail above.Other ways of projecting the radiation into the polymer may be used,including embodiments in which, for example, a digital data projector, adiascope, or an overhead projector having an appropriate radiationwavelength, may be used to dispose a non-printing image on the floor ofthe polymer plate by projecting the radiation through a masking element.Thus, the source 1540 may take the form of a point source, planarsource, linear source, compound source, or any type of radiation sourceknown in the art, having any dimension, without limitation.

Although the additional back exposure forming non-printing images may beapplied before, during or after main and back exposure of the polymerprinting plate, it is preferred to apply the additional exposure afterthe primary back and main exposure have been performed, and even morepreferred to apply the additional exposure after the primary backexposure but before the front exposure. The latter preference arisesbecause transparency of the polymer for UV light increases after thepolymer is cured. Accordingly, after the primary back exposure, more UVradiation can be concentrated at the layer inside the polymer that isslightly above the plate floor. For the same reason, it is advantageousto perform the main (front) exposure after the primary and additionalback exposure steps, to reduce the impact of the additional exposureenergy at the printing surface of the plate. The invention is notlimited to any particular order of the back exposure, non-printinginformation exposure, and main (front) exposure steps. Each cumulativeexposure applied in connection with the total exposure for each maycomprise a plurality of partial exposure steps, and thus, the sequenceof exposures may include any permutation of sequences of partialexposure steps.

An advantage of this embodiment for providing non-printing informationin the floor of the plate is the ability to control the thickness or thelevel the non-printing structures relative to the floor level moreprecisely as compared the methods for creating such structures usingmicrodots in the mask. In some embodiments, the floor structures createdby the foregoing methods may comprise continuous 3-dimensionalstructures, comparable to embossed structures, and not composed ofmicrodots.

Although described primarily herein above in configurations in which thenon-printing features are raised above the floor a lesser amount thanthe printing features, it should be understood that the non-printingfeatures may also be in the form of depressions relative to the floor.In such configurations, the apparatus and methods as described above maybe implemented to create a first, subfloor level using the primaryexposure, and then using the additional radiation to create the floor ata level above the subfloor. Thus, the non-printing features will remainat the height of the subfloor at a desired distance below the floor.

The various controllers depicted herein may be programmed withmachine-readable instructions, which instructions may reside on anynon-transitory computer readable storage medium, including but notlimited to a hard disk, a flash drive, a server in the cloud, ordistributed among multiple locations “on the cloud” and on a localnetwork. The instructions may include a first set of instructions forimaging a first plurality of printing dots defining a screened image formaking printing structures on a flexographic printing plate via exposureto actinic radiation from a front side of the printing plate, and asecond set of instructions for imaging non-printing indicia via exposureto actinic radiation from a back side of the printing plate, includingby any of the methods and using any of the systems as described above.The non-printing indicia made by the back-exposure methods and systemsmay define any of the structures as discussed anywhere herein, includingfeatures selected from the group consisting of: alphanumeric characters,non-text graphics, a machine readable code, a line, and combinations orrepeating patterns of any of the foregoing

Test Strips

In many cases, plates are placed on a cutting table for separatingdifferent plate patches from another, and in some cases, also to cut offthe test strip or any other markings not intended for printing. In apreferred embodiment, reproducing code 214 on the back of the plateidentical to code 212 may be performed using a laser, such as, e.g. a10.6 μm CO2 Laser or a fiber laser emitting in the mid-infrared range(e.g. a 2 μm Thulium laser), such as in a range of wavelengths between1.8 and 2.5 μm, and in one preferred embodiment, 2.03 μm. The laser,such as coupled to a laser Galvo scanner, removes the positive ornegative portions corresponding to the QR-code image, thus providing thebinary differences detectable by a reader. Thus, code 212 may first beread in its first location on the top side 202 of plate 200 on the teststrip 210 prior to cutting off the test strip 210, then the code may betransferred to a non-printing location in the floor 204 of the plate ina location inside the image region 205 of the plate.

In one embodiment, the test strip and/or the code contains a testpattern that allows plate quality to be checked, such as a check with aconfocal microscope, after processing of the plate, to determine if theplate processing was successful such that the plate may be approved forprinting.

Another embodiment may comprise two identical test strips 210, one ofwhich (not shown) may be cut off and sent separately from the plate to aproofing service, while the rest of the plate is sent to the printer. Insuch an embodiment, positive proofing of the test strip may be aprerequisite for the printer to start to print the plate. This methodmay prevent printing of plates having artifacts, thus saving moneyassociated with failed prints. Identification information for processingthe test strip and the printing plate may be established by the code.

In still another embodiment, the process data may be stored in the plateby means of a strip at the side of the plate, the strip containing apattern of spots, such as, for example, “high” spots having a firstelevation (e.g. reaching the plate printing surface), and “low” spotshaving a second elevation (e.g. below the plate printing surface). Inother embodiments, the high spots may have a first relatively lesserdistance below the plate printing surface, and the low spots may have asecond relatively greater distance below the plate printing surface. Thespot sequence represents a digital data “word” comprising sequences ofhigh and low bits, like in a serial data transmission. The data wordcontains the information to be stored in the plate. Thus, for example,the code may be stretched out along a run length of the plate but havingonly a very narrow width. The advantage of this type of code, ascompared to a standard 2D code such as a bar code or QR code, is thatthe code only requires a small stripe near the image, which makes iteasier to add when not much space free of images is available on theplate. Such a code, in principal, is similar to a very long bar code,but able to carry more information because of its length. For example,the corresponding reader may sense dark/light contrast or distance fromthe reader due to length of travel of a beam from the reader to thesurface of the high or low spots, or may use laser triangulation sensorsor computer image evaluation. A preferred reader is configured as aswipe code scanner in which the scanner is stationary while the platewith the code moves along under the scanner. In some embodiments, amechanical sensor capable of sensing the difference between the relativeelevations of high and low spots may read the code as the sensor headmoves in accordance with the dot elevation. Another aspect of theinvention includes monitoring the status of the workflow by software ina central computer, such as computer 170 depicted in FIG. 1 . Eachprocess stage 110, 120, etc. sends information to the central computerafter scanning the code from the polymer, such as reporting the time andplace of arrival of the plate and the current processing status. Thusthe actual status of a job in the workflow can be determined immediatelyand exactly from the central computer. Certain plates may thus beidentified and located instantly in the company workflow. The centralcomputer 170 is programmed with software capable of processing all thisinformation of different plates from different stages of production,such as for example the ESKO Device Manager. The code or indicia mayalso be read in-between process steps or after completion of the processsteps, such as in a storage area or in a queue awaiting processing.

Mobile Device Readers

In another embodiment, the information stored in the indicia may bescanned and read by application software running on a mobile device,such as a mobile phone or tablet computer. As is known in the art,systems incorporating such mobile devices typically include a firstportion of software running on the mobile device, with the mobile devicein communication with a server over a communication network, such as awireless network, wherein a second portion of the software resides onthe server and interfaces with the portion on the mobile device. Such asystem permits immediate identification of plates anywhere in theworkflow, including for example, identifying the location of plates instorage dedicated for reprint jobs. In an exemplary method, such as thatdepicted in FIG. 2A, reader 220, such as a mobile phone, may scan thecode on the plate and then provide process parameter information to anoperator, such as on the display 222 of the phone or on the displayassociated with a user interface corresponding to the process equipment(110, 120, etc.) relating to the current processing step. The operatormay then enter the relevant process parameters into the processequipment for the next process step, if that equipment is not incommunication with the scanning means to read process parametersautomatically.

Device Manager

One aspect of the invention comprises controlling and coordinating thevarious process steps in a way that the overall process is optimized intime and efficiency. Aspects of the claimed invention include not onlyproviding process parameters to the processing machines (110, 120, etc.)for the various pre-press process stages in the workflow of making aflexo plate, but also providing real-time monitoring of the overallplate manufacturing process using readers 220 communicating thein-process locations of a plurality of plates in accordance with scans.Thus, a central tracking processor or “device manager” 170 may receiveupdates continuously during all process steps of the workflow and thusmay be capable of providing a real-time plot of each plate's currentposition in the entire plate workflow. As used herein, the term“real-time” is intended to mean providing current informationcontemporaneously, subject to routine delays inherent in thecommunication protocols, processor speeds, and display renderingcapabilities of the various components of the system. In someimplementations, in addition to location information, process qualityfeedback may also be communicated to the Device Manager 170. The DeviceManager 170 may be integrated into, for example, Automation Enginesoftware from Esko, the Applicant of the present invention. Althoughcertain specific workflow steps have been mentioned, it should beunderstood that the indicia may include information relating to otherprocessing machines or process steps in addition to those describedexplicitly herein, and may, for example, cover any or all process stepsbetween order intake at least until storage after printing orreprinting, which may be applicable for printers who make their ownplates. The process is not limited to any number of steps, however, andthus in some embodiments, the process may cover fewer or more steps.

Exemplary Processes

Thus, one aspect of the invention comprises a process for making a flexoplate. A flowchart corresponding to an exemplary process is depicted inFIG. 3 . The process may have a plurality of process steps, such as atleast an imaging step, a curing step, a washing step, a cutting step, aprinting step, and a storage step, each step performed by a processingmachine having at least one variable operating parameter. It should beunderstood that some processes do not require a cutting step. In someprocesses, plates are discarded after the printing step and are notstored. Thus, the cutting and storage steps are optional, depending uponthe process. Furthermore, it should be understood that not every processstep may require instructions for every plate, and thus, some indiciamay embody instructions for fewer than all of the process steps. Ingeneral, however, at least some embodiments of the invention embodyinstructions for more than one process step in the workflow. The term“variable operating parameter” means any parameter that may varydepending upon the plate or job, and thus the processing machinerequires some input for control of the processing. Step 300 comprisesproviding machine-readable indicia on the flexo plate. Themachine-readable indicia is preferably configured to provide readabilitydownstream of the washing and cutting steps without printing in theprinting step. Providing the machine readable indicia comprisesembodying in the indicia information including at least a plateidentifier and instructions corresponding to the at least one variableoperating parameter for each of the processing machines or embodying inthe indicia an address in computer storage where such informationresides. Step 310 comprises reading the indicia from the flexo plateusing a reader in communication with at least a controller of each ofthe processing equipment configured to perform one of the process steps.Step 320 comprises providing information about the location of the platein the workflow to a tracking controller. Step 330 comprises processingthe plate with the processing machine using the at least one variableoperating parameter embodied in the indicia or stored at the addressembodied in the indicia. The order of steps 320 and 330 may be reversed.Steps 310-330 may then be repeated for subsequent machines or processsteps in the workflow. In some cases, reading the indicia in step 310and reporting the information to the tracking controller in step 320 maybe performed by a reader that is not associated with a processingmachine, such as a mobile device, for reporting a location of the plateintermediate of process steps, in storage, or in transit. The processmay include in step 350 providing real-time tracking of workflowposition for each of the plurality of in-process flexo plates. This stepmay be practiced at any time during the process after receivinginformation from the one or more readers in the workflow.

The indicia may be configured to embody quality information indicativeof printing properties associated with the plate, in which case“processing” the plate in step 330 may comprise proofing the printingplate by analyzing the quality information embodied in the indicia.

Although the invention is not limited to any particular information orinstructions embodied in the machine-readable indicia, each process stepmay have certain parameters that are particularly well suited forimplementation using embodiments of the invention. For example, in amounting step, the indicia may contain information indicative of thephysical position of the plate/slug/patch on a substrate or printingsleeve (e.g., flexo plate left printing lane/middle printing lane/Rightprinting lane). The indicia may also contain information indicative ofthe physical coordinates for the mounting cameras of the mountingdevice. Similarly, in a curing step, such as a UV curing step, theinstruction may provide UV exposure parameters, such as exposure time,intensity, and the like. In a “washing” or othernon-cured-polymer-removal step, the instructions may comprise processingparameters such as temperature, time, and type (water, solvent,thermal). In a plate-cutting step, the instructions may include thecorresponding cut file and cutting parameters, such as type of cuttingblade, thickness and type of the substrate to be cut, and the like. In aquality control step, the instructions may include instructions forloading a specific portion of the plate under process to a device forconducting a quality control (QC) evaluation, along with information forverification relative to information detectable using the device. Forexample, the evaluation device may be a monitor in which the loadedinformation is an image of the portion of the plate that can be viewedby the human operator, or the device may be a sensor for measuring plateheight or dot shape or size, and the measured value may be automaticallycompared against a stored value. QC steps may be performed at any pointin the workflow. In the printing step, the parameters may include anyspecialized inks to use, color curves to apply, as well as instructionsregarding what location of the printed result should be the subject of aQC evaluations using the onboard machine vision system, such as systemsmade by AVT, a subsidiary of Danaher Corporation.

Any number of other process parameters may be included instead or inaddition, and the invention is not limited to any particular processparameters for any particular process step, nor does each indicianecessary contain information corresponding to each process step. Itshould be noted that although discussed herein in the context of asingle indicia, the amount of data to be stored may exceed what ispractical to embed in a single instance of certain types of indicia.Accordingly, multiple indicia may be used, and the information embeddedin first indicia may comprise the coordinates for the location of secondindicia with instructions for a particular step of interest. Asindicated in step 300, the indicia may be initially placed in a firstlocation, in which the process further comprises the optional step 340of conducting at least one processing step with the indicia in the firstlocation, then reading the indicia with a first reader after thatprocessing step, and reproducing the indicia in a second location priorto the printing step. This optional step may be particularly useful whenthe first location is, for example, on a test strip that is later cutaway in a cutting step, and the second location is in a floor of theplate in an image area of the plate, as described herein.

Although certain aspects of the invention are particularly useful andadvantageous in a flexo environment, the disclosure herein is notlimited to any particular type of plate or processing.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A process for making a flexo plate, the processcomprising providing non-printing indicia disposed on a floor of theplate using areas of presence and absence of polymer in the plate floor,wherein the non-printing indicia are disposed on a floor of the plate,the process comprising: forming the non-printing indicia via exposure toactinic radiation from a back, non-printing side of the plate, includingproviding a primary back exposure and an additional back exposure, theprimary back exposure provided by a first exposure source and theadditional back exposure performed by a second exposure source, whereinthe non-printing indicia comprise areas of presence of polymer raisedabove the plate floor, and the process comprises forming the plate floorusing the primary back exposure, and forming the areas of presence ofpolymer raised above the plate floor in the non-printing indicia usingthe additional back exposure.
 2. The process of claim 1, wherein theprimary back exposure is performed before the additional back exposure.3. The process of claim 2, further comprising providing printingfeatures disposed on the floor of plate via front side exposure, whereinthe additional exposure is performed after the primary back exposure butbefore the front side exposure.
 4. The process of claim 1, wherein thefirst exposure source and the second exposure source are spaced apartfrom one another in a fixed relationship, and the process comprisescausing relative movement between the plate and the first and secondexposure sources.
 5. The process of claim 4, further comprisingproviding printing features disposed on the floor of plate via frontside exposure, wherein the front side exposure is provided by a thirdexposure source spaced from a front side of the plate in a fixedrelationship relative to the first and second exposure sources.
 6. Theprocess of claim 1, wherein the additional back exposure is provided byan LED matrix comprising a plurality of individual LED units.
 7. Theprocess of claim 1, wherein the additional back exposure is provided bydirecting radiation to an imaging plane disposed above the plate floor.8. The process of claim 1, comprising forming the non-printing indiciaas continuous embossed structures.
 9. The process of claim 1, whereinthe additional back exposure is provided using a digital lightprocessing (DLP) unit.
 10. The process of claim 1, wherein theadditional back exposure is provided by directing radiation from one ormore sources through a masking component having holes, transparent, orrelatively more translucent areas for permitting the additional backexposure through the masking component, and solid, opaque, or relativelyless translucent areas for blocking the additional back exposure. 11.The process of claim 10, wherein the additional back exposure and theprimary exposure are provided simultaneously.
 12. The process of claim10, wherein the additional back exposure is provided in a different stepthan the primary exposure.
 13. The process of claim 10, wherein themasking component comprises a liquid crystal diode (LCD) matrix.
 14. Theprocess of claim 10, wherein the masking component comprises a film. 15.The process of claim 10, wherein the additional back exposure isperformed over an area of the plate smaller than an entire area of theplate, the process comprising selecting the area of the plate forreceiving the additional back exposure to avoid the non-printing indiciainterfering with printing features.
 16. The process of claim 1, whereinthe non-printing indicia are selected from the group consisting of:alphanumeric characters, non-text graphics, a machine readable code, aline, and combinations or repeating patterns of any of the foregoing.17. A system for making a flexo plate by curing a photopolymer platewith actinic radiation, the system comprising a front side exposuresystem configured to direct actinic radiation to a front side of theprinting plate for creating printing features defined above a floor ofthe plate, and a back side exposure system configured to direct primaryactinic radiation and additional actinic radiation to a back side of theprinting plate for creating the floor and non-printing features raisedrelative to the floor, wherein the non-printing features are raisedabove the plate floor but configured not to affect printability of theprinting features, the back exposure system comprising a primary backside radiation source configured to provide the primary actinicradiation for forming the plate floor and an additional back sideradiation source configured to provide the additional actinic radiationfor forming the non-printing features of the non-printing indicia raisedabove the plate floor.
 18. The system of claim 17, wherein the backexposure system comprises an LED matrix comprising a plurality ofindividual LED units configured to emit at least the additional actinicradiation.
 19. The system of claim 18, further comprising opticsconfigured to focus radiation from the LED matrix to a desired planerelative to the plate.
 20. The system of claim 19, wherein the desiredplane is above the plate floor.
 21. The system of claim 17, wherein theprimary back side radiation source and the additional back sideradiation source are spaced apart from one another at a first spacing ina fixed relationship, the system further comprising means for causingrelative movement between the plate and the primary and additional backside radiation sources.
 22. The system of claim 21, wherein the frontside exposure system comprises a front side radiation source spaced froma front side of the plate in a fixed relationship at a second spacingrelative to the primary back side radiation source and the means forcausing relative movement is further configured to cause movementbetween the plate and the front side radiation source.
 23. The system ofclaim 22, wherein the first spacing and second spacing are adjustable.24. The system of claim 17, wherein the back exposure system comprises aDLP matrix configured to supply the additional actinic radiation. 25.The system of claim 17, wherein the back exposure system comprises asource of actinic radiation and a masking component disposed between thesource and the plate, wherein the source is configured to emit actinicradiation toward the masking component and the masking component isconfigured to transmit the additional actinic radiation to the plate.26. The system of claim 25, wherein the masking component comprises aliquid crystal diode (LCD) matrix.
 27. The process of claim 25, whereinthe masking component comprises a film.
 28. The process of claim 25,wherein the source comprises a plurality of individual LED unitsarranged in an LED matrix configured to cover a full length and width ofthe plate and to emit both the primary actinic radiation and theadditional actinic radiation to the back side of the printing plate. 29.The system of claim 17, wherein the back exposure system comprises anLED matrix comprising a plurality of individual LED units configured toemit both the primary actinic radiation and the additional actinicradiation to the back side of the printing plate.
 30. The system ofclaim 29, wherein the LED matrix defines a linear source configured toprovide the actinic radiation over a full first dimension of the plateand less than a second full dimension of the plate, wherein the systemfurther comprising means for causing relative movement between the plateand the LED linear source along the second dimension of the plate.
 31. Anon-transitory computer readable storage medium having data storedtherein a first set of instructions for imaging a first plurality ofprinting dots defining a screened image for making printing structureson a flexographic printing plate via exposure to actinic radiation froma front side of the printing plate and a second set of instructions forimaging non-printing indicia via exposure to actinic radiation from aback side of the printing plate, the non-printing indicia raised above afloor of the printing plate and configured not to affect printability ofthe printing structures, the non-printing indicia defining one or morefeatures selected from the group consisting of: alphanumeric characters,non-text graphics, a machine readable code, a line, and combinations orrepeating patterns of any of the foregoing, the second set ofinstructions configured to cause a primary back side radiation source toprovide primary actinic radiation for forming the plate floor and anadditional back side radiation source to provide additional actinicradiation for forming the one or more features of the non-printingindicia raised above the plate floor.